Rocker arm ratio

[postal]

I was told that there are 3 standard stage 2 rocker arm ratios. 1.55, 1.64, 1.70.

I will be ordering a custom hydraulic roller through comp as soon as I figure out exactly what I want. Comp has more than half a dozen lobe profiles around 220 degrees duration. 220 is the duration range I decided to go with. Now heres my question:

What is harder on the valve train, getting the lift your looking for in the lobe or getting it with higher ratio rocker arms? Depending on how aggressive the lobe is and which rocker ratio I choose I can get a 220 or so lobe with any where from .512 to .578 lift.

I'm looking for a low maintenance valve train. I don't want to have to change valve springs all the time and stuff like that. So should I go with a low lift lobe and a higher rocker ratio or vice versa? If it was up to me right now I would just go middle of the road with both because I not sure.

This cam will be for a 270" stage 1 short block with ported stage 2 heads.

P.S: any input on lobe separation angle? I leaning towards 112 to 114.

TIA: Jason

 

[QuickWrench]

Assuming you're talking about a roller cam, I'd go with a lower rocker ratio. The higher ratio rockers are a touch easier on the cam and lifters, but play hell on the rockers themselves, and can be harder on the valve tips as well. You won't notice much of any difference in the valve spring maintenance either way.

 

[65vette396]

Just as QuickWrench said, it doesn't matter how you achieve the lift, rather it be via rocker arm ratio or actual lobe lift, it will impose the same strain on the upper valvetrain. Lift is what kills the springs, just go slightly higher in Duration and less on lift. Drew

 

[QuickWrench]

Just another quick note...

It's ALWAYS in your best interest to invest in the best quality springs that you can find, even if they're more than you planned to spend. A set that costs double or triple the cost of a run-of-the-mill set will pay for itself many, many times over in maintenance, reliability, and performance.

For example, on the Brad Anderson motors we run in the Pro Mod car, we've made a change to titanium springs that cost over a grand a set. Previously, we were servicing/replacing the springs after 6 or 8 runs. The ones we have now are lasting 4 to 5 races, which can be as much as 25 runs. The initial cost is about twice as much, but we're getting four to five times the life, and we're not worrying about dropping a valve at 9,800 RPM. The lash stays put, the pressures stay even, and they DON'T BREAK.

Here's some good reading on the subject, also:
http://www.rehermorrison.com/techTalk/03.htm

 

[postal]

Would it be a good idea to just go with the 1.64 rockers and a lobe that will give me around .548" lift?

Quickwrench:
What kind of springs should I look into for a 550 or so lift cam and 7000 rpm limit?

Thanks: Jason

 

[QuickWrench]

Originally posted by postal
Would it be a good idea to just go with the 1.64 rockers and a lobe that will give me around .548" lift?

Quickwrench:
What kind of springs should I look into for a 550 or so lift cam and 7000 rpm limit?

Thanks: Jason

In reality, I'd go with whatever quality rocker set you can get a deal on. Neither of the ratios you listed is really that big of a deal, and you're not trying to get an inch of lift out of the thing.

Spring-wise...the cam manufacturer will let you know what opened/closed spring pressures you'll need. From there, it depends on your heads, but I'd call Bill Anderson or somebody with a lot of Stage II-specific spring seat and height info. I really don't know who out there puts out the most kick-@ss springs that fit these motors, but he or Dan Strezo would. My real point with the previous post was soap-boxing the spring issue. I've seen too many dollars flushed and races lost by scrimping on upper-valvetrain parts.

 

[EightSecV6]

To be honest, if you are going to use a hydraulic roller, ANY ratio rocker will be fine if it is T&D or Jesel. The lobe lift is a concern, it is matched to your performance goal and combination. MOST of the time we spec the cams out around the rockers that the customer already has because new ones are not reall readily available (affordable!)I use Comp springs on all the hydraulic stuff and K Motion for the solids.

 

[chevyII]

I had heard Isky makes good springs?

 

[GARY HARVEY]

Springs/Lift/Ratio question

IMO... PSI has an excellent offering for Springs

High Lift Profile causing excessive coil bind KILLS springs.
With this in mind, getting valve lift from high ratio rockers is a trend along with longer stems & taller springs and a new set of covers (mo mony). Then you get to jack up the rockers too.

I thought BMS (Chapman) heads rocker ratio was determined by design. I mention this because the only ratio my BMS S2 heads can use are the 1.70s. {This info comes from the Chapman people and Larry Torres (T&D).}

You may save yourself some pain by sending (USED rockers) to T&D and have them checked for wear. Used Busch Series valve train parts are WELL used.

I favor having springs cryo'ed and coated, courtesy of a vendor of your choice. Saving a few $s and valve train preparation doesn't equate.

I have fallen from the soap box.